Disperse Dyes for Poly(Lactic Acid) Based Fibers

ABSTRACT

The present invention relates to the use of a yellow and/or a red and/or a blue component of disperse dyes for dyeing poly(lactic acid) fibers or poly(lactic acid) based fibers.

The present invention relates to the use of disperse dyes for dyeing poly(lactic acid) fibers and poly(lactic acid) based fibers comprising fiber mixtures of poly(lactic acid) fibers and other fibers, for example aromatic polyester fibers.

Poly(lactic acid) fibers are non-petroleum based fibers for which hydrocarbons of vegetable origin are used as the raw material and which can be recycled in the ecological system by being degraded to water and carbon dioxide in the natural environment. Consequently, they are excellent materials in the environment where there is a shift away from petroleum depletion and the reuse of the resources is facilitated. Furthermore, when compared with other biodegradable materials such as aliphatic polyesters it has a high fusion point and glass transition point and it is also as strong as general-purpose aromatic polyesters and so its widespread future use as practical fibers can be anticipated. Use as an industrial resource material, as an interior and living resource material and as fibers for clothing purposes in the form of films, sheets, span-bonded material, resins and fibers has been considered, and the manufacturers are making rapid progress with developments which will extend the scope of application (for example, see Japanese Unexamined Patent Application Laid Open HB-311781 and Japanese Unexamined Patent Application Laid Open 2003-49374).

Dyes with which this material can be dyed with excellent light fastness properties will be needed if these new materials are to be widely used as fibers for automobile interior decoration and in interior applications, but as yet no dyes with which this can be achieved satisfactorily have appeared.

The present invention is based upon an understanding of the actual situation indicated above and is intended to provide disperse dyes with which the color fastness on poly(lactic acid) based fibers in particular is good and which have a good balance regarding light fastness among the three primary color dyestuffs, which form green and orange and also brown and grey, resembling the extents of fading of the respective dyestuffs.

The inventors have realized disperse dyes which meet the above mentioned requirements and which especially have good light fastness and dyeing properties by selecting and specifying from among the many dyestuffs which exist those dyestuffs which have comparatively good light fastness and build-up properties on poly(lactic acid) based fibers and combining these dyestuffs.

The present invention thus claims the use of a yellow component comprising at least one dyestuff of the group consisting of structural formulae (1), (2), (3), (4) and (5)

wherein R¹ is (C₁-C₃) alkyl and R² is (C₄-C₇) alkyl;

wherein n is 0 or 1;

wherein R³ is (C₁-C₃) alkyl or 2-hydroxyethyl;

and/or a red component comprising at least one dyestuff of the group consisting of structural formulae (6) and (7)

wherein one of R⁴ and R⁵ is hydrogen and the other is hydroxyethoxyethyl, hydroxybutoxypropyl, acetoxyethoxyethyl or acetoxybutoxypropyl;

wherein R⁶ is hydrogen or methyl; and/or a blue component comprising at least one dyestuff of the group consisting of structural formulae (8), (9) and (10)

wherein one of R⁷ and R⁸ is nitro and the other hydroxyl and R⁹ is hydrogen, chlorine or 2-hydroxyethyl;

wherein R¹⁰ is methoxypropyl, ethoxypropyl or methoxyethoxypropyl;

for dyeing poly(lactic acid) fibers or poly(lactic acid) based fibers.

The present invention thus provides disperse dyes and mixtures of disperse dyes with which dyeing with good light fastness can be carried out on poly(lactic acid) fibers.

In the definitions for the dyestuffs of the formulae (1) to (10 given above

(C₁-C₃) alkyl groups can be straight-chain or branched and are preferably methyl, ethyl, n-propyl and iso.propyl.

(C₄-C₇) alkyl groups can also be straight-chain or branched and are preferably n-butyl, i-butyl, sek.-butyl, tert.-butyl, pentyl, hexyl or heptyl.

In the dyestuff of the formula (8) R⁹ is preferably hydrogen atom or 2-hydroxy-ethyl.

According to the present invention it is preferred to use only one of the dyestuffs of the formulae (1) to (10) for dyeing poly(lactic acid) fibers or poly(lactic acid) based fibers.

However, it is especially preferred to use a mixture comprising two or three of each of the yellow, the red and the blue dyestuffs.

In addition, it is also especially preferred to use a mixture comprising a yellow component comprising at least one of the dyestuffs of the formulae (1), (3) and (4), a red component comprising at least one dyestuff of the formula (6) and a blue component comprising at least one dyestuff of the formula (8).

It is also preferred to use one or more dyestuffs of the formulae (1) to (10) conjointly with an ultraviolet absorber. Such ultraviolet absorbers are known to the skilled person, are described in literature and are available in the market place. Usually such ultraviolet absorbers are triazine- benzotriazole- or benzophenone-based. Examples are the products sold by Ciba Specialty Chemistry, Switzerland, under the tradename Cibafast.

The dyestuffs of the formulae (1) to (10) are insoluble or sparingly soluble in water and so for dyeing poly(lactic acid) based fibers using the dyestuff mixtures of this invention a dye bath or printing paste where they have been dispersed in the form of fine particles in an aqueous medium using a naphthalenesulfonic acid/formaldehyde condensate, higher alcohol fatty acid ester, higher alkylbenzenesulfonate or the like as a dispersant is prepared and the dyeing can then be carried out by the dip-dyeing method, the pad-dyeing method or by the dye-printing method. The dip-dyeing method in particular is preferred. If, in the case of dip-dyeing, the usual dye-treatment methods such as the high temperature dyeing method, the carrier dyeing method, the thermosol dyeing method and the like are applied then good dyeing can be achieved with poly(lactic acid) fibers or fiber mixtures in which they are included. Poly(lactic acid) fibers are weak in respect of heat and alkaline conditions when compared with polyester fibers and so high temperature dyeing at from 110 to 120° C. for from 15 to 30 minutes with a dye liquid pH of from 4.0 to 5.0 with the conjoint use of triazine-based, benzotriazole-based or benzophenone-based ultraviolet absorber is especially desirable.

Within the present invention the term poly(lactic acid) based fibers is understood to comprise mixtures of poly(lactic acid) fibers and other fibers. Such other fibers are preferably aromatic polyester fibers such as polyethylene terephthalate, polypropylene terephthalate or polybutylene terephthalate fibers. Mixtures of propylene terephthalate fibers and poly(lactic acid) fibers are especially preferred.

The invention is described in more practical terms below by means of examples and comparative examples, but the invention is not limited by these examples.

EXAMPLES 1 TO 19

The dyestuffs represented by the structural formulae (1-1), (1-2), (1-3), (2-1), (2-2), (3), (4-1), (4-2), (5), (6), (7-1), (8-1), (8-2), (8-3), (8-4), (9-1), (9-2), (9-3) and (10) indicated below were each mixed with twice the weight of naphthalenesulphonic acid/formaldehyde condensate and disperse dyes were obtained by finely grinding and drying in the usual way. Poly(lactic acid) containing fibers (5 g) produced by the Toray Co., Japan were immersed in the dye bath which had been prepared by weighing out just the amount of disperse dye for about ½ N dyed material in the case of a single color and a total concentration of about ⅓ N dyed material in the case of a compound color with respect to the standard dye concentration specified in JIS L 0808 for to 5 g of poly(lactic acid) fibers, adding the triazine based “Cibafast P” produced by the Ciba Specialty Chemical Co. as an ultraviolet absorber and dye promotor in an amount of 2% (o.w.f) and acetic acid/sodium acetate pH buffer solution (pH 4.5) to the dye bath and making up to a total of 100 ml with salt-free water, and dyeing was carried out by maintaining the bath at a temperature of 110° C. for 30 minutes. The dyed materials obtained were subjected to a reducing wash in 150 ml of water which contained 2 g/l of sodium hydrosulfite, 2 g/l of sodium carbonate and 1 g/l of Hostapal LFB Conc. produced by the Clariant Co. by maintaining a temperature of 65° C. for 10 minutes.

wherein R⁴ and R⁵ are defined as given above

The light-fastness of each dyed material was measured in accordance with the light fastness test specification of the Toyota Automobile Co. and the results obtained were as shown in Table 1.

Moreover, the light fastness test was carried out using a High Energy Xenon Fadometer produced by the Suga Testing Machine Co. for the testing apparatus under conditions of black panel temperature 73±3° C. with irradiation using the 38 cycle (182 hour) illumination method with 3.8 hours illumination time/1 hour dark time per cycle. The tests were carried out with a test cloth lined with urethane. The JIS L 0804 fading gray scale was used for assessing the grade. TABLE 1 Structural Hue of the Light Fastness Example Formula Dyed Cloth (Grade) 1 (1-1) Yellow  3-4+ 2 (1-2) Yellow 3-4 3 (1-3) Yellow 3-4 4 (2-1) Yellow 4+ 5 (2-2) Yellow 4-5 6 (3) Yellow 4+ 7 (4-1) Yellow 4  8 (4-2) Yellow 3-4 9 1:1 Mixture of Yellow  3-4+ (3) and (4-2) 10 (5) Yellow 3+ 11 (6) Red 4− 12 (7) Red 3+ 13 (8-1) Blue  3-4+ 14 8:2 mixture of Blue 3-4 (8-1) and (8-2) 15 (8-3) Blue 3-4 16 (8-4) Blue 3-4 17 1:1 mixture of Blue 3-4 (9-1) and (9-2) 18 (9-3) Blue 3-4 19 (10) Blue 3-4

COMPARATIVE EXAMPLES 1 TO 6

The dying of poly(lactic acid) based fibers was carried out in the same way as in the examples 1 to 19 using disperse dyes which had been prepared using the yellow dyestuff (A-1) and (A-2), the red dyestuffs (B-1) and (B-2) and the blue dyestuffs (C-1) and (C-2) of which the structural formulae are indicated below which have excellent light fastness on polyester fibers.

(B-1) is a 1:1 mixture of the two dyestuffs below

The results of the light fastness tests of these dyestuffs are given in Table 2. TABLE 2 Structural Hue of the Light Fastness Example Formula Dyed Cloth (Grade) 1 (A-1) Yellow 2  2 (A-2) Yellow 2− 3 (B-1) Red 1-2 4 (B-2) Red 2+ (blue modified color) 5 (C-1) Blue 1-2 6 (C-2) Blue 1-2

As becomes clear from Tables 1 and 2, the dyed materials obtained in Examples 1 to 19 were seen to have very much better light fastness when compared with the dyed materials obtained with the Comparative Examples 1 to 6.

EXAMPLES 20 TO 31

Dyeing was carried out in accordance with the examples given below using mixtures of disperse dyes as indicated in Table 3, which had been prepared using the dyestuffs of the structural formulae [1-1], [2-2], [3], [4-1], [4-2], [5], [6], [8-1], [8-3], [9-1], [9-2] and [10] as described above. However, the benzotriazole based Sunlife LP250 produced by the Hibana Chemical Co. was used for the ultraviolet absorber. The numerical values indicated as amounts compounded in the table are in units of wt %. TABLE 3 Example Formula 20 21 22 23 24 25 26 27 28 29 30 31 (1-1) 40 16 36 (2-2) 3 5 (3) 16 25 (4-1) 50 21 23 31 39 (4-2) 24 23 23 48 (5) 23 (6) 18 13 17 14 17 17 13 10 17 61 41 (8-1) 32 26 59 25 27 34 31 69 59 (8-3) 54 30 54 1:1 Mixture of 5 4 (9-1) and (9-2) (10) 7 Hue of dyed Cloth Brown Brown Grey Grey Brown Grey Brown Grey Brown Green Orange Violet Light Fastness 3-4− 3 3-4 3+ 3-4 3-4 2-3 3 3-4− 3-4− 3-4− 3-4−

COMPARATIVE EXAMPLES 7 TO 13

The dyeing of poly(lactic acid) based fibers was carried out in the same way as in the examples 20 to 31, but using dyestuffs of examples 20 to 31 and dyestuffs (A-1), (A-2), (B-1), (B-2), (C-1) and (C-2) as given in Table 4 below. TABLE 4 Comparative Example Formula 7 8 9 10 11 12 13 [1-1] [2-2] [3] 8 [4-1] [4-2] [5] [6] 23 12 [8-1] 43 60 33 [8-3] 45 1:1 Mixture 5 10 of [9-1]/ [9-2] [10] 5 [A-1] 48 77 50 45 [A-2] 63 42 [B-1] 9 4 5 17 [B-2] 22 16 [C-1] 10 15 [C-2] 19 4 Hue of Dyed Brown Gray Brown Gray Brown Gray Brown Cloth Light 1-2 2− 1 1-2 1-2 1-2 1 Fastness

EXAMPLE 32

Dyeing was carried out in accordance with Example 20 except that the fibers used in Example 20 were replaced with a poly(lactic acid) fiber/polypropylene terephthalate fiber (50150 wt %) mixture, the dyeing conditions were changed to 120° C.×40 minutes and the ultraviolet absorber was changed to benzophenone based Sunlife LPS855 produced by the Hibana Chemical Co. The results were such that the light fastness of the dyed material obtained was excellent at grade 4. 

1-7. (canceled)
 8. A dyed poly(lactic acid) fiber or poly(lactic acid) based fiber material which has been dyed with a yellow component comprising at least one dyestuff of the group of the structural formulae (1), (2), (3), (4) and (5)

wherein R¹ is (C₁-C₃) alkyl and R² is (C₄-C₇) alkyl;

wherein n is 0 or 1;

wherein R³ is (C₁-C₃) alkyl or 2-hydroxyethyl;

and/or a red component comprising at least one dyestuff of the group of structural formulae (6) and (7)

wherein one of R⁴ and R⁵ is hydrogen and the other is hydroxyethoxyethyl, hydroxybutoxypropyl, acetoxyethoxyethyl or acetoxybutoxypropyl;

wherein R⁶ is hydrogen or methyl; and/or a blue component comprising at least one dyestuff of the group of structural formulae (8), (9) and (10)

wherein one of R⁷ and R⁸ is nitro and the other hydroxyl and R⁹ is hydrogen, chlorine or 2-hydroxyethyl;

wherein R¹⁰ is methoxypropyl, ethoxypropyl or methoxyethoxypropyl;


9. The dyed fiber as claimed in claim 8, wherein a mixture comprising two or three of each of the yellow, the red and the blue dyestuffs is used.
 10. The dyed fiber as claimed in claim 8, wherein a mixture comprising a yellow component comprising at least one of the dyestuffs of the formulae (1), (3) and (4), a red component comprising at least one dyestuff of the formula (6) and a blue component comprising at least one dyestuff of the formula (8) is used.
 11. The dyed fiber as claimed in claim 8, which further comprises an ultraviolet absorber is used conjointly with of each of the yellow, the red and/or the blue dyestuffs.
 12. The dyed fiber as claimed in claim 10, which further comprises an ultraviolet absorber is used conjointly with of each of the yellow, the red and/or the blue dyestuffs.
 13. The dyed fiber as claimed in claim 8 wherein a poly(lactic acid) based fiber is dyed which comprises a mixture of poly(lactic acid) and an aromatic polyester fiber is used.
 14. The dyed fiber as claimed in claim 12 wherein a poly(lactic acid) based fiber is dyed which comprises a mixture of poly(lactic acid) and an aromatic polyester fiber is used. 